Systems and methods for absorbing waste electricity from regenerative braking in hybridized vehicles

ABSTRACT

The invention relates to a system for absorbing electric energy from regenerative braking. The system includes a battery, a thermoelectric module in thermally-conductive contact with the battery, a generator for generating an electric current from regenerative braking, the generator connected to the battery via a first switch and connected to the thermoelectric module via a second switch, and a sensor for measuring a temperature and a charge state of the battery. The system also comprises a controller for activating and deactivating the first switch and the second switch when certain conditions have been met.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 12/242,776, entitled “SYSTEMS AND METHODS FOR ABSORBING WASTEELECTRICITY FROM REGENERATIVE BRAKING IN HYBRIDIZED VEHICLES,” filed onSep. 30, 2008, now U.S. Pat. No. 8,035,349, the entire disclosure ofwhich is hereby incorporated by reference herein.

BACKGROUND

1. Field

The invention relates to systems and methods for absorbing electricenergy or waste electricity from regenerative braking in hybridizedvehicles. More particularly, the invention relates to systems andmethods for using thermoelectric devices to absorb electric energy orwaste electricity from regenerative braking in hybridized vehicles.

2. Background

The term “hybrid vehicle” is commonly referred to as a vehicle thatutilizes more than one power source for propulsion. For example, ahybrid vehicle can be a vehicle that uses an internal combustion engineas a primary power source and an electric motor as a secondary powersource. The electric motor can operate independently of or inconjunction with the internal combustion engine to drive the wheels ofthe vehicle. The electric motor enhances the fuel efficiency of theinternal combustion engine.

The electric motor can be powered by a number of batteries that need tobe recharged on a regular basis. The batteries can be used to drive theelectric motor and other components of the vehicle. The batteries aregenerally high-voltage (200-400 volts) batteries. A generator may beused to charge the batteries.

Upon deceleration or downhill driving of a hybrid vehicle, the generatorcreates energy by regenerative braking and transfers the energy to thebatteries for charging. Regenerative braking has the effect of slowingthe vehicle down when traveling on a flat surface and reducingacceleration of the vehicle when traveling downhill. The batteries arecontinuously charged by regenerative braking.

Continuously charging the batteries by regenerative braking has severaldrawbacks. First, the batteries can reach or exceed a predeterminedmaximum state-of-charge. Second, the batteries can reach or exceed apredetermined maximum temperature. In both cases, the batteries cannotaccept any additional charge or risk being damaged from overcharging oroverheating. Therefore, the amount of electric energy that can beabsorbed by the batteries from regenerative braking may be limited dueto the afore-mentioned drawbacks. If the batteries cannot absorb theenergy from regenerative braking, the generator may be disengaged andthe slowing or retarding force to the vehicle is reduced or eliminated.

Therefore, a need exists in the art for providing systems and methods toabsorb electric energy or waste electricity from regenerative braking inhybridized vehicles.

SUMMARY

In one embodiment, the invention is a system for absorbing electricenergy from regenerative braking. The system comprises a battery, athermoelectric module in thermally-conductive contact with the battery,a generator for generating an electric current from regenerativebraking, the generator connected to the battery via a first switch andconnected to the thermoelectric module via a second switch, and one ormore sensors for measuring a temperature and a charge state orstate-of-charge of the battery. The system also comprises a controllerfor deactivating the first switch and activating the second switch whenthe charge state is equal to or greater than a maximum charge state ofthe battery, wherein the electric current is transferred to thethermoelectric module and has a polarity that causes the thermoelectricmodule to alternately cool and heat the battery in order to absorb theexcess energy and change battery temperature if needed. The alternatingmay be performed every 5 seconds, for example.

The system also comprises a controller for (1) deactivating the firstswitch and activating the second switch when the battery temperature isequal to or greater than a maximum temperature of the battery, whereinthe electric current is transferred to the thermoelectric module and hasa polarity that causes the thermoelectric module to cool the battery,(2) deactivating the first switch and activating the second switch whenthe battery temperature is below a minimum battery temperature, whereinthe electric current is transferred to the thermoelectric module and hasa polarity that causes the thermoelectric module to heat the battery,and (3) deactivating the first switch and activating the second switchwhen the charge state is equal to or greater than a maximum charge stateof the battery, wherein the electric current is transferred to thethermoelectric module and has a polarity that causes the thermoelectricmodule to alternately heat and cool the battery to absorb the excesselectric current without changing the charge or net state of thebattery.

In another embodiment, the invention is a method of absorbingelectricity from regenerative braking. The method includes measuring anactual temperature of a battery using a first sensor, measuring a chargestate of the battery using a second sensor, and obtaining a maximumoperating battery temperature and a maximum charge state from memory.The method also includes transferring electric current from regenerativebraking to a thermoelectric module using a controller wherein thecontroller sets a polarity of the electric current to cool the batterywhen the actual temperature is greater than or equal to the maximumoperating battery temperature, and transferring electric current fromregenerative braking to the thermoelectric module using the controllerwherein the controller alternates a polarity of the electric current toheat and cool the battery when the charge state is greater than or equalto the maximum charge state.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of the invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, wherein:

FIG. 1 is a block diagram of a system that uses thermoelectric modulesto absorb waste electricity from regenerative braking according to anembodiment of the invention; and

FIG. 2 is a flow chart of a method of absorbing waste electricity fromregenerative braking according to an embodiment of the invention.

DETAILED DESCRIPTION

Apparatus, systems and methods that implement the embodiments of thevarious features of the invention will now be described with referenceto the drawings. The drawings and the associated descriptions areprovided to illustrate some embodiments of the invention and not tolimit the scope of the invention. Throughout the drawings, referencenumbers are re-used to indicate correspondence between referencedelements.

FIG. 1 is a block diagram of a system that uses thermoelectric modulesto absorb waste electricity from regenerative braking according to anembodiment of the invention. The system 100 may include an engine 105,an electric motor/generator 110, a controller 115, a sensor 120, abattery 125, and a thermoelectric module 130. The system 100 may be usedwith a vehicle that has a transmission 135, a braking system 140, andwheels 145. The vehicle may be an automobile powered by any means (e.g.,fuel cells, gasoline, hydrogen, solar, etc.) provided the vehicle isfully or partially powered by one or more batteries. For example, thevehicle may be a hybrid vehicle having a propulsion system which uses acombustion engine as one source of power, either to drive the vehiclewheels through a direct mechanical link or to generate electrical power,and also uses an electric motor to provide some or all propulsion powerfor the vehicle wheels.

The engine 105 can be an internal combustion engine, a fuel cell, or anyother type of engine that may be hybridized to provide partial or fullpower to the vehicle. The engine 105 is connected to the transmission ortorque converter 135, which is connected to an axle 150 that rotates tomove the wheels 145.

The electric motor/generator 110 can be combined as one component or canbe separate components. The electric motor/generator 110 uses electricfields and coiled wires to provide or generate electrical current topower the vehicle.

The sensor 120 measures the actual temperature of the battery 125 anddetermines the charge state (e.g., fully or partially charged) of thebattery 125. The sensor 120 is in thermally-conductive contact with thebattery 125.

The battery 125 can be a lead-acid battery, a nickel cadmium battery, anickel metal hydride battery, a lithium-ion battery, or any other typeof battery. The battery 125 may be a 12 volt battery for powering thecomponents of the vehicle or a high-voltage battery for powering theelectric motor/generator 110. Other voltages may also be used. Thebattery 125 may comprise one or more batteries of the same or differentvoltages.

The thermoelectric module 130 may have a first side and a second side.The flow of electrical current in one direction through thethermoelectric module 130 causes the first side to be heated and thesecond side to be cooled. Conversely, the flow of electrical current inthe opposite direction through the thermoelectric module 130 causes thefirst side to be cooled and the second side to be heated. The first orthe second side of the thermoelectric module 130 is inthermally-conductive contact with the battery 125. In one embodiment,the thermoelectric module 130 is a Peltier circuit.

The controller 115 can be any type of controller or switch which candirect the electrical current produced by the electric motor/generator110 to the battery 125 and/or the thermoelectric module 130 based on thebattery temperature and/or the battery charge received from the sensor120. That is, if the actual battery temperature exceeds a desirableoperating temperature of the battery 125, then the controller 115 maycause the electric current generated from regenerative braking to bedirected to the thermoelectric module 130 in a direction of current flowthat cools the battery 125. If the actual battery temperature is lessthan a desirable operating temperature of the battery 125, then thecontroller 115 may cause the electric current generated fromregenerative braking to be directed to the thermoelectric module 130 ina direction of current flow that heats the battery 125. Similarly, ifthe charge state is fully charged, then the controller 115 may cause theelectric current generated from regenerative braking to be directed tothe thermoelectric module 130 in an alternating direction of currentflow that serves to cool and heat the battery 125 in periodic or randomfashion. The controller 115 may be coupled to a memory 117, which can beused to store a maximum operating battery temperature and a minimumoperating battery temperature, and a fully-charged state of the battery125.

The controller 115 can cause the electric motor/generator 110 tosimultaneously direct electric waste energy to both the battery 125 andthe thermoelectric module 130 to preserve the “engine braking” feel. Inone embodiment, the thermoelectric module 130 can consume additionalenergy from regenerative braking to preserve the “engine braking” feelby alternately heating and cooling the battery 125 in rapid succession(e.g., every 5 seconds). The alternately heating and cooling of thebattery 125 may also be periodic or random.

FIG. 2 is a flow chart of a method of absorbing waste electricity fromregenerative braking according to an embodiment of the invention. Thesensor 120 measures an actual temperature and a charge state of thebattery 125 (block 200). The controller 115 receives the actualtemperature and the charge state of the battery 125. The controller 115also receives and/or stores a maximum battery temperature and a minimumbattery temperature (block 205). If the actual temperature of thebattery 125 is greater than the maximum battery temperature (i.e.,battery 125 is too hot) or less than the minimum battery temperature(i.e., battery 125 is too cold) (blocks 210 and 220), then thecontroller 115 causes the electric motor/generator 110 to transferelectric current (i.e., waste electricity from regenerative braking) tothe thermoelectric module 130 in a direction or with a polarity thatcools or heats the battery 125 (blocks 215 and 225). If the charge stateof the battery 125 is fully charged (i.e., battery 125 does not need anymore charging) (block 230), then the controller 115 causes the electricmotor/generator 110 to transfer electric current (i.e., wasteelectricity from regenerative braking) to the thermoelectric module 130in a direction or with a polarity that cools or heats the battery 125depending on the actual temperature of the battery 125 (block 235). Inone embodiment, if the charge state of the battery 125 is fully charged,then the controller 115 causes the electric motor/generator 110 totransfer electric current to the thermoelectric module 130 in adirection or with a polarity that alternately (e.g., every 5 seconds)cools and heats the battery 125. If the charge state of the battery 125is not fully charged (i.e., battery 125 needs more charging), then thecontroller 115 causes the electric motor/generator 110 to transferelectric current to the battery 125 and/or the thermoelectric module 130in a direction or with a polarity that charges the battery 125 and/orcools or heats the battery 125 depending on the actual temperature ofthe battery 125 (block 240).

Directing the electricity from regenerative braking to thethermoelectric module 130 (rather than continuously charging the battery125) allows the vehicle to preserve its original retarding force insteadof reducing its rolling resistance and forcing the driver toincreasingly rely on the braking system 140 for slowing the vehicle. Thesystem 100 maintains or acquires optimum temperature of the battery 125.In addition, the thermoelectric module 130 provides a sink for orabsorbs waste electricity or excess power during periods of time when(1) regenerative braking energy continues to be created after thebattery 125 has reached its maximum charge state, (2) the battery 125 isoverheating due to, for example, extended downhill driving, and (3) thebattery 125 is too cold because the battery 125 has been exposed to coldtemperatures.

Those of ordinary skill would appreciate that the various illustrativelogical blocks, modules, and algorithm steps described in connectionwith the examples disclosed herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the disclosed apparatus and methods.

The various illustrative logical blocks, modules, and circuits describedin connection with the examples disclosed herein may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theexamples disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anApplication Specific Integrated Circuit (ASIC). The ASIC may reside in awireless modem. In the alternative, the processor and the storage mediummay reside as discrete components in the wireless modem.

The previous description of the disclosed examples is provided to enableany person of ordinary skill in the art to make or use the disclosedmethods and apparatus. Various modifications to these examples will bereadily apparent to those skilled in the art, and the principles definedherein may be applied to other examples without departing from thespirit or scope of the disclosed method and apparatus. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive and the scope of the invention is, therefore,indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A method of absorbing energy from regenerativebraking, comprising: sensing a charge state of a battery; transferringan electric current from the regenerative braking to a thermoelectricmodule; adjusting a polarity of the electric current to control a heattransfer between the thermoelectric module and the battery when thesensed charge state is less than or equal to a maximum charge state ofthe battery; and adjusting the polarity of the electric current to causethe thermoelectric module to absorb heat from the battery when thesensed charge state is greater than the maximum charge state of thebattery.
 2. The method of claim 1, further comprising: transferring theelectric current from the regenerative braking to the battery when thesensed charge state is equal to or less than the maximum charge state ofthe battery; and terminating the electric current transfer from theregenerative braking to the battery when the sensed charge state isgreater than the maximum charge state of the battery.
 3. The method ofclaim 1, further comprising: sensing a temperature of the battery; andadjusting the polarity of the electric current to a first polarity tocause the thermoelectric module to absorb heat from the battery when thesensed temperature is equal to or greater than a maximum operatingtemperature of the battery.
 4. The method of claim 1, furthercomprising: sensing a temperature of the battery; and adjusting thepolarity of the electric current to a second polarity to cause thethermoelectric module to transfer heat to the battery when the sensedtemperature is equal to or less than a minimum operating temperature ofthe battery.
 5. The method of claim 1, further comprising: sensing atemperature of the battery; and adjusting the polarity of the electriccurrent to be at a first polarity or a second polarity based on thesensed temperature, to cause the thermoelectric module to exchange heatwith the battery when the sensed temperature is between a maximumoperating temperature of the battery and a minimum operating temperatureof the battery.
 6. The method of claim 5, wherein: the first polarity ofthe electric current causes the thermoelectric module to absorb heatfrom the battery, and the second polarity of the electric current causesthe thermoelectric module to transfer heat to the battery.
 7. A methodof regulating a temperature of a battery for use in regenerativebraking, the method comprising: transferring an electric current fromthe regenerative braking to the battery; sensing the temperature of thebattery; transferring the electric current from the regenerative brakingto a thermoelectric module; and adjusting a polarity of the electriccurrent to enable the thermoelectric module to absorb heat from thebattery when the sensed temperature is equal to or greater than amaximum operating temperature of the battery.
 8. The method of claim 7,further comprising: adjusting the polarity of the electric current toenable the thermoelectric module to transfer heat to the battery whenthe sensed temperature is equal to or less than a minimum operatingtemperature of the battery.
 9. The method of claim 7, furthercomprising: adjusting the polarity of the electric current to enable thethermoelectric module to cool or heat the battery based on the sensedtemperature when the sensed temperature is between a maximum operatingtemperature and a minimum operating temperature of the battery.
 10. Themethod of claim 7, further comprising: transferring the electric currentfrom regenerative braking to the battery when the charge state is lessthan or predetermined charge state of the battery; and terminating theelectric current transfer from regenerative braking to the battery whenthe charge state is greater than or equal to the predetermined chargestate of the battery.
 11. The method of claim 10, wherein thetransferring the electric current to the battery includes activating aswitch connecting a generator and the battery.
 12. The method of claim10, wherein the terminating the electric current to the battery includesdeactivating a switch connecting a generator and the battery.
 13. Amethod of absorbing electricity from regenerative braking, comprising:measuring an actual temperature of a battery using a first sensor;measuring a charge state of the battery using a second sensor; obtaininga maximum operating battery temperature and a maximum charge state frommemory; transferring electric current from the regenerative braking to athermoelectric module using a controller wherein the controller sets apolarity of the electric current to cool the battery when the actualtemperature is greater than or equal to the maximum operating batterytemperature; and transferring electric current from the regenerativebraking to the thermoelectric module using the controller wherein thecontroller alternates a polarity of the electric current to heat andcool the battery when the charge state is greater than or equal to themaximum charge state.
 14. The method of claim 13 further comprisingobtaining a minimum operating battery temperature from the memory andtransferring electric current from the regenerative braking to athermoelectric module using the controller wherein the controller sets apolarity of the electric current to heat the battery when the actualtemperature is less than or equal to the minimum operating batterytemperature.
 15. The method of claim 13 further comprising activating afirst switch that connects the battery to a generator when the actualtemperature is greater than a minimum operating battery temperature. 16.The method of claim 15 further comprising activating a second switchthat connects the thermoelectric module to the generator when the actualtemperature is less than the minimum operating battery temperature. 17.The method of claim 13 further comprising activating a first switch thatconnects the battery to a generator when the actual temperature is lessthan the maximum operating battery temperature.
 18. The method of claim17 further comprising activating a second switch that connects thethermoelectric module to the generator when the actual temperature isgreater than the maximum operating battery temperature.
 19. The methodof claim 13 further comprising activating a first switch that connectsthe battery to a generator when the charge state is less than themaximum charge state.
 20. The method of claim 19 further comprisingactivating a second switch that connects the thermoelectric module tothe generator when the charge state is greater than the maximum chargestate.